Imagine thinking that Yoda just not ever involving himself into anything is more interesting. That would definitely make him quite hypocritical when he says “Do, or do not, there is no try”. He doesn’t say, “You’re better off just watching everything bad happen from a distance and not do anything about it.” Him knowing Anakin more personally is way more impactful and makes for a better narrative, instead of him just sitting out as the entire galaxy goes to shit. Like wow, what a great hero.
Well then, maybe it should be that he can’t go back, because he’d be arrested and killed if he ever returned (either by the Jedi or by the Republic/Empire). He wanted to go back and help, but he knew the Jedi wouldn’t accept his help and that he could not face these threats head-on. Maybe he’s a bit more pragmatic, seeing a frontal assault on the Emperor as a terrible idea. If he falls, there are few-to-no options left.
He doesn’t really need to know Anakin either, since he has clairvoyant abilities that he’s honed over a long lifespan. He can pick up the gist of what happens through his remaining connections to the Jedi (i.e., Qui-Gon, Obi-Wan, and the people who exiled him).
It’s not the EU that “rehabilitated” them, he just learned between the movies. It’s established in Revenge of the Sith that he became Qui-Gon’s apprentice, it doesn’t take much to realize that the change in his character between the prequels and the originals was because his perspective changed during his exile. There’s not even any EU stuff that covers what Yoda did between ROTS and ESB. Guess who also had character development between films? Luke, between ESB and ROTJ.
True, but I think it enhances Yoda’s stock as a character if he wasn’t a part of the Jedi during the Clone Wars or during the fall of the Jedi. He’s an “alternate path” for Luke, a contrast to Obi-Wan. Obi-Wan tried to work within the crumbling Jedi system and screwed up, while Yoda’s teachings cannot provide the full story. Therefore, Luke takes the third option - his own interpretations of his masters’ lessons combined with his life experiences.
He didn’t say “Don’t underestimate the Emperor’s ability to manipulate people”, he said “The powers of the Emperor.” It’s a clear foreshadowing to his force lightning anyway, as the moment Luke lets his guard down and underestimates the Emperor, he gets attacked by force lightning. Force lightning is the payoff to all the talk of the Emperor being someone you don’t underestimate. And Yoda knew this, because force lightning was how he lost.
It could also be that he read about that power and knows that powerful Sith lords can use it. He could have seen it through the Force or dealt with a dark side pupil that tried to adopt this ability. He doesn’t need first-hand knowledge.
While the force is still very spiritual in the prequels, the overall quality of the fights and styles of combat in AOTC and ROTS really lose me. It just feels a lot more “fake,” in a way that I can’t really articulate. I get the whole “Jedi at the height of their power” thing, but the fighting doesn’t nearly have the same emotional resonance (IMHO) as it did in the OT or ST (or even the animated shows).
I also maintain that the biggest flaw with the prequels is a fundamental one: they were made with the assumption that people have seen the OT. Getting them to work in episode order requires writing them with the assumption that nobody has seen the OT.